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From:   Suman Ghosh <sumang@marvell.com>
To:     Shigeru Yoshida <syoshida@redhat.com>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "dsahern@kernel.org" <dsahern@kernel.org>,
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CC:     "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [EXT] [PATCH net v2] ipv4: ip_gre: Avoid skb_pull() failure in
 ipgre_xmit()
Thread-Topic: [EXT] [PATCH net v2] ipv4: ip_gre: Avoid skb_pull() failure in
 ipgre_xmit()
Thread-Index: AQHaJTq+xdxLhbQE0EyCVUEj9YjahLCXIVzg
Date:   Sun, 3 Dec 2023 06:58:19 +0000
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References: <20231202161441.221135-1-syoshida@redhat.com>
In-Reply-To: <20231202161441.221135-1-syoshida@redhat.com>
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Hi Shigeru,

>diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index
>22a26d1d29a0..5169c3c72cff 100644
>--- a/net/ipv4/ip_gre.c
>+++ b/net/ipv4/ip_gre.c
>@@ -635,15 +635,18 @@ static netdev_tx_t ipgre_xmit(struct sk_buff *skb,
> 	}
>
> 	if (dev->header_ops) {
>+		int pull_len =3D tunnel->hlen + sizeof(struct iphdr);
>+
> 		if (skb_cow_head(skb, 0))
> 			goto free_skb;
>
> 		tnl_params =3D (const struct iphdr *)skb->data;
>
>-		/* Pull skb since ip_tunnel_xmit() needs skb->data pointing
>-		 * to gre header.
>-		 */
>-		skb_pull(skb, tunnel->hlen + sizeof(struct iphdr));
>+		if (!pskb_network_may_pull(skb, pull_len))
[Suman] Since this is transmit path, should we add unlikely() here?
>+			goto free_skb;
>+
>+		/* ip_tunnel_xmit() needs skb->data pointing to gre header. */
>+		skb_pull(skb, pull_len);
> 		skb_reset_mac_header(skb);
>
> 		if (skb->ip_summed =3D=3D CHECKSUM_PARTIAL &&
>--
>2.41.0
>